This is the ultimate swim coach stopwatch with it's 300 split memory and waterproof case, the Seiko S141 stopwatch is what you need.
The Seiko S141 Stopwatch can store and recall up to 300 split/lap times. Dual memory mode - choose to store multiple events in memory or store times from only the most recent event. Memory can be recalled during operation. Measures strokes per minute. Large three row display. Time and calendar, battery life indicator, 10-bar water resistant (waterproof)
Available now at Swim T3 - your local swim and triathlon store.